Shaver



y 1941. o. c. KAVLE 2,240,890

SHAVER Filed Oct. 11, 1958 3 Sheets-Sheet 1 0 UjfaI/Ze y ,1941 I o. c.KAVLE' I 2,240,890

SHAVER Filed Oct. 11, 1958 3 Sheets-Sheet 2 O. C. KAVLE May6, 1941.

SHAVER Filed Oct. l1, 1938 {is E 9 9 f v I l 3 Sheets-Sheet 3 PatentedMay 6, 1941 UNITED STATES PATENT OFFICE SHAVER Oscar C. Kavle, Syracuse,N. Y.

Application October 11, 1938, Serial No. 234,451

6 Claims.

This invention appertains to shaving devices, and more especially, to animproved razor embodying relatively reciprocal blades as distinguishedfrom rotary or oscillatory blades. The invention readily lends itself topower operation, and more particularly, to operation by an electricalmotor, although it is to be understood that certain of the featuresthereof have equally great utility irrespective of the type of operatinginstrumentalities which may be availed of, as will hereinafter be morefully apparent.

One of the primary objects of the invention is to provide a razor of theclipper type which is endowed with a materially improved shaving qualityand produces a closer and cleaner shave than hasheretofore been possiblewith the power driven shavers now on the market. In practically all ofthe power operated shavers which are available at the present date,considerable difiiculty is experienced in obtaining a close anduniformly clean shave, especially at the commencement of use thereoffollowing long use of the so called safety or straight razors. In otherwords, it has been found that the hairs have to have time enough toadapt themselves to the power driven razors before a reasonably closeshave can be even approximately obtained, and this time may varyanywhere from several months to a year or more. My new razor has beenfound to be fully effective at all times, and regardless of thecondition of the hairs resulting from the previous use of other types ofrazors.

Another difiiculty which is particularly experienced in the use of thepresent day shavers heretofore available is that they will not give aclean shave if the hairs are allowed to grow relatively long. As amatter of fact, some of the shavers will not cut long hairs at all, andothers only if great pains are taken and considerable time is expendedin the manipulation of the shaver so that the individual hairs areremoved bit by bit. My new shaver completely avoids these difficulties,and will cleanly out long as well as short hairs, and with a minimum ofeffort and expenditure of time.

A further object of the invention is to provide a pair of relativelyreciprocal blades in combination with a special guard or guidawhich isso arranged in relation to the blades as to permit the blades to bebrought into close contact with the skin at the base of the hairs, andto be drawn over the skin with a. smooth and pleasant feeling andwithout scratching, abrading or otherwise injuring even the most tenderskin.

A still further object of the invention is to provide an improvedassembly of relatively reciprocal clipper blades which are maintainedunder a uniform tension so that the same will cleanly sever the hairsrelatively closer to the skin than has heretofore been possible, and atleast one of drive the relatively reciprocal blades of the shaver,

said motor assembly being preferably of unitary compact form adapted tobe housed within a hollow handle, upon one end of which the relativelyreciprocal blades are adapted to be mounted.

The motor is further characterized by its simplicity of construction,few parts and freedom from wear and the necessity for periodicadjustments or repair.

Other and further objects and advantages of the invention will behereinafter described, and

the novel features thereof defined in the appended claims.

In the drawings:

Figure 1 is a View in elevation of an electrically operated razorembodying my invention;

Figure 2 is an enlarged plan view of the razor shown in Figure 1 withthe head and one side of the handle or motor casing removed to show themanner in which the motor is mounted, portions of the motor being brokenaway to better disclose the interior construction thereof;

Figure 3 is a longitudinal sectional view through the complete assemblyof the motor and casing therefor, substantially at right angles to theview in Figure 2, the motor being shown in elevation;

Figure 4 is a transverse sectional view, taken on the line 4-4 of Figure2;

Figure 5 is an enlarged longitudinal sectional View, taken through thehead end of the shaver,

and illustrating the blade assembly and the mounting head therefor;

Figure 6 is a sectional view, taken approximately on the line B6 ofFigure 5;:

Figure 7 is a sectional view, taken on the line 1-1 of Figure 6;

Figure 8 is a transverse sectional view, taken on the line 8-8 of Figure5;

Figure 9 is a view in side elevation of the motor assembly, andparticularly illustrating its unitary compact form;

Figure 10 is a view in elevation of one of the complementary halves ofthe two-part motor casing which constitutes the handle for the shaver,the same being viewed towards the interior thereof and Figure 11 is asectional view, taken approximately on the line I l-ll of Figure 2.-

Like reference characters designate corre sponding parts in the severalfigures of the drawings. As shown in Figure 1, the shaver in itselectrically driven form for use as a razor preferably comprises ahousing, generally designated I, of any suitable shape and size, whichmay be conveniently grasped in one hand of the user so as to constitutea handle. At one end of the handle I, provision is made for receiving anelectrical connector plug 2 for connecting the conductor cord 3 leadingfrom the source of electrical energy to the terminals of the motor,which has been generally designated 4 in Figure 9. At the opposite endof the handle or motor casing I, there is mounted a cutter head,generally designated 5, said cutter head including a pair of relativelyreciprocal blades or shear plates which are driven by the motor in amanner hereinafter more specificall described.

The handle or casing I is preferably of twopiece construction so as toprovide two similar complementary halves, each of which is suitablyhollowed out and recessed for receiving the various parts of the motorassembly, as will be best understood from reference to Figures 2, 3, 4and 10. The complemental handle sections are adapted to be securedtogether in back to back relation by means of suitable fastenings 6,which may have the form of small tie-bolts having removable heads 6threaded thereon and suitably r socketed or recessed in the handle, thetie-bolts passing through apertures 1 formed in the respective halves ofthe handle. The handle is preferably made of insulating material such ashard rubber, Bakelite, or the like, which can be conveniently molded inthe shape and form desired. At one end of each of the handle sections,there is provided a recess 8 of generally rectangular form and a pair ofsemi-circular grooves or recesses 9, as best shown in Figure 10, theformer providing a socket II) for the reception of the electricalconnector plug 2 when the two halves of the handle are assembledtogether, and the latter receiving the shanks II-, II of the motorterminals I2, I2. Accordingly, when the handle is assembled with themotor assembly 4 and terminals I2, I2 enclosed therein, the terminalsact as dowels and serve to restrain the sections of the handle I againstrelative transverse displacement.

At the opposite end of each of the handle sections, there is providedanother generally rectangular recess I3, which leads inwardly to thehollow central portion of each section and affords a space to permitfree movement of the operating lever I4 of the motor assembly.

The motor assembly comprises a. laminated core I5, having the generalconfiguration of the letter E, and upon the central leg I6 of the core,there is mounted a spool or form I! of suitable winding I8. At each sideof the laminated core I5, there is provided a side plate I9, having anarm 20 overlapping the long side of the laminated core I5, the sideplates being suitably secured to the core as by means of three rivets 2|extending transversely through both plates and the intermediate corelaminations, as will be best understood from reference to Figures 2, 3and 9. The side plates I9, I9 together constitute a frame for the motorarmature, and they are suitably apertured as at 22, 22 for the receptionof the tiebolts 6, 6 which extend through the handle I. Extendingtransversely between the plates I9, I9,

and suitably secured to the same, are three abutment members ofcylindrical form, respectively designated 23, 24 and 25, and which arearranged in spaced relation to each other with their central axes lyingat the apexes of a triangle. As seen in Figure 2, the abutment member 25lies substantially directly above the abutment member 23, and theabutment member 24 is displaced laterally respecting both abutmentmembers 23 and 25 and lies substantially midway therebetween. Thepurpose of this arrangement of the abutment members will now bedescribed.

The motor armature 26 is disposed beside the laminated core I5 so as toextend across the legs of the core, the forward end of the armaturebeing laterally offset, as at 21, and terminating in the operating leverI4, which is preferably an integral part of the armature and disposedsubstantially centrally of the corresponding end of the motor casing orhandle I. To this end, the outer leg 28 of the core I5 is shorter thanthe other legs to permit the offset 21 of the armature 26 so as todispose the operating lever I4 substantially at the center of the end ofthe casing I as previously described.

The opposite end of the armature 26 is of substantially Uform, and theshort leg 29 thereof is adapted to be received between the abutmentmembers 23 and 25 on the inner side and the abutment member 24 on theouter side. Each of the abutment members 24 and 25 is provided with atransversely disposed set-screw 30, 3|, respectively, which isadjustable to firmly clamp the leg 29 of the armature 26 between theabut ment members in an obvious manner, the adjustment being preferablysuch that the main or central portion of the armature 26 is normallydisposed in slightly spaced relation to the free extremities of the legsof the core I5 (see Figures 2 and 9). The spacing may be varied bysuitably loosening one of the set-screws 30, 3I and tightening theother, as will be obvious.

Suitable electrical connection is made between the terminals I2, I2 andthe winding I8, as by fastening short relatively stiff pieces of Wire32, 32 to the terminals I2, I2 at one end, with the wires disposed alongone side of the motor assembly and terminating at their opposite endsnear the winding I8. One end of the winding I8, which is normallycomposed of many turns of relatively fine wire, is connected to theadjacent end of one of the stiff wires 32, as at 33, and the other endof the winding is connected to the adjacent end of the other stiff wire32, as at 34. A piece of suitable insulating sheet material 35 ispreferably interposed between the wires 32 and the contiguous frameplate I9 of the motor assembly to prevent grounding or short-circuitingof the winding I8, one end of the insulating material 35 being benttransversely, as at 35, to extend across the end of the motor assemblybetween the latter and the terminals I2, l2, The insulating material 35,36 may be fastened in place by placing another small piece 31 or thesame material over the wires 32 at the opposite side to the piece 35 andsecuring the two together by suitable fastening instrumentalities 38,which may or may not be fixed to the adjacent frame plate I9.

It will be observed that when the winding I8 is energized, as byconnecting the motor terminals I2, I2 to the plug 2 on the end of theconductor 3 which leads to a source of alternating electrical energy,the armature 26 will be set into motion, causing the operating lever [Ato re- ;ciprocate back and forth within the opening formed by therecesses I3 in the ends of the handle or motor case sections. It will beunderstood, of course, that the armature is constructed of metal whichwill be influenced by the magnetic field established by the winding l8through the core I5, and the armature is of such size and resilientcharacteristic as to permit the same to flex back and forth at its fixedend which is clamped between the abutments 23, 24 and 25, the ab-utment23 constituting the fulcrum.

In order to r minimize vibration of the laminations of the core 15,additional rivets 39 and 40 may be extended respectively through thecenter leg l6 near its free extremity and through the'base of the shortleg 28. The rivet 40 has preferably mounted on its opposite ends at theside of the core I5 a pair of sleeves or collars 4|, which will thusbecome rigidly assembled onto the core so as to project at oppositesides thereof.

Each of the motor casing or handle sections is provided with a recess 42for receiving the corresponding collar 4|, so that when the motor isassembled in the handle and the two halves of the handle are securedtogether by the fastenings 6, S, the collars 4| will act as dowels andpositively prevent the outer end of the core from moving within thehandle. This construction is especially advantageous where thefastenings 6, 6 which extend through the handle I are located relativelycloser to the terminal end of the motor than to the operating lever endthereof, and the entire assembly can thus be made rigid even though notmore than two tie-bolts 6, 6 are employed to hold the assembly together.It will be accordingly understood that the construction herein shown anddescribed materially contributes to ease of assembly of the motor withinthe handle and removal of the same from the handle. Moreover, the motormay be completely assembled into a unitary form before it is placed inthe handle or casing I, as will be best understood from reference toFigure 9.

To prevent any likelihood of the operating lever end of the motorarmature 26 from striking the short leg 28 of the core l5 and producingan objectionable noise, buffer means is preferably provided to cushionthe armature. This buffer means, as shown in the drawings, comprises asmall block 44 of resilient material, such as rubber, cork or the like,the same being mounted in a generally U-shaped frame 45 which isslidable in an opening 55 extending inwardly of each of the handlesections at the parting line (see Figures 2, l and 11). An adjustingscrew 41, disposed in a threaded opening 48 correspondingly formed inthe handle sections at the parting line, serves to adjustably projectthe buffer material 44 to the desired inward position limiting themovement of the armature to the desired amount, which falls short ofpermitting the armature to engage the leg 28 of the core. The bufferaccordingly contributes to the quietness of operation of the motor,which incidentally does not have any parts which tend to wear out or getout of order.

As previously described, the cutter head is mounted on the end of thehandle or motor casing l, opposite to the socket H1 in which theterminals l2 are disposed, the cutter head being a rigid body composedof a good quality hardened metal and being generally T-shaped intransverse cross-section, as will be best understood from reference toFigure '7. The head 5 is preferably removably attached to the handle Iby means of screws 49 extending through apertures 50 in each of thecomplemental handle sections, there being preferably a pair of screwsdisposed in each side of the handle, with their inner extremitiesthreadedly received in opposite ends of the spaced transverse openings5l in the leg 52 of the head 5, as will be best understood fromreference to Figures 6 and 8, inclusive. The head is further providedvwith a central opening 53 extending perpendicularly with respect to thethreaded openings 5|, 5 I, and disposed midway therebetween. Thisopening 53 is of sufficient size to afford clearance for the operatinglever 54 of the motor unit 4 and to permit the operating lever to freelyreciprocate within the same without interference. When the head 5 ismounted on the handle I, its outer end lies slightly inwardly withrespect to the outer extremity of the operating lever M, as shown'inFigure 5. Extending lengthwise across the outer face of the head 5 is ashallow recess 54 of sul stantial width, and transversely spacedtherefrom at opposite sides of this recess 54 is a pair of generallyU-shaped grooves 55, 55, also extending lengthwise of the head 5 andbeing of substantial depth. By virtue of the construction justdescribed, there is provided on the outer end of the head 5 a pair oftransversely spaced shoulders 56, 56 having flat faces which constitutebearing surfaces for one of a pair of relatively reciprocal blades orshear plates designated 51.

The material of the head 5 at the outer sides of the grooves 55, ispreferably rounded off, as at 58 to provide a. smooth curved surface.The outwardly extending rounded marginal ribs 59 resulting from theremoval of the material to form the grooves 55, 55 constitute guards orguides when brought into engagement with the skin from which the hair isto be removed, and thus preventing the cutter blades from biting intothe skin or otherwise scratching or abrading the same, as willhereinafter become more fully apparent. The ribs 59, 55 are preferablytransversely slotted to a depth approximately half the depth of theslots 55, 55, the transverse slots being designated 60 and beingdisposed relatively close together to create a comb effect, as will beunderstood from reference to Figures 1, 6 and '1.

The cutting or clipping action of the shaver is created by a pair ofrelatively reciprocal blades or shear plates, as previously described,one of the blades or shear plates being the member 51 above referred to.This blade or shear plate 51 is of flat and relatively rigid form,having its opposite longitudinal edges beveled, as at 6!. At the centerof the blade, there is a slot 62 for snugly receiving the upperextremity of the operating lever l4. Adjacent to each of the oppositeends of the blade 51 is a slot 63, having their major axes disposedlengthwise of the blade and constituting guide slots as hereinafterdescribed. The longitudinal edges of the blade 51 are serrated toprovide laterally projecting teeth 64 having any suitable pitch, as forexample, on the order of .030. The edges of the teeth 64 are preferablybeveled so that the opposed edges of any tWo adjacent teeth convergetowards the outer face of the blade opposite to the face which bearsagainst the bearing surfaces 56, 56 of the head 5. From the foregoing,it will be understood that the blade 51 is adapted to berapidly'reciprocated by the motor unit 4 through the me dium of theoperating lever l4, and the blade 51 is of such width as tosubstantially overhang the grooves 55, 55 in the outer end of the head5, as will be best seen in Figures 6 and '1.

At the outer side of the blade or shear plate 51 and bearing against thesame, is another blade or shear plate 65, which is fixed againstmovement in a manner now to be described. The blade 65 is flexible,resilient and normally transversely arcuate. The opposite longitudinaledges of the fixed blade 65 are provided with flat surfaces 66 at theinner side of the blade so that when the blade 65 is mounted against theblade 51, the longitudinal edges of the blades will be in substantiallyfiat contact with each other for a substantial distance transverselyinwardly from the edges of the respective blades. The fiat faces 66 arepreferably formed by lapping the blade while held in a jig or fixtureunder the same contact tension which it is intended to have whenassembled with the blade 51. The fixed blade 65 has its longitudinaledges also serrated to provide teeth 61, the edges of which arepreferably beveled oppositely to the teeth 54 of the blade 51, as willbe best understood from reference to Figure 6. The pitch of the teeth 61is preferably slightly less than the pitch of the teeth 64, being on theorder of .025, the purpose of this being to prevent the cutting orshearing action of the relatively reciprocal blades from taking placesimultaneously at each tooth, and thereby affording an improved cuttingaction and reducing the load on the motor unit to a minimum. The lappedsurfaces 66 on the inner side of the blade 65 preferably extend inwardlyfrom the opposite longitudinal edges of the blade for a distanceapproximately equal to the depth of the teeth 61.

The blade 65 is mounted upon the head 5 and held stationary by means ofa keeper plate 68 which is of substantial thickness to insure rigidity.The keeper plate is transversely arcuate at its inner side 68', but thearc of this side of the keeper plate preferably has a slightly greaterradius than the arc of the blade 65 when in its normal untensionedcondition. Thus, when the keeper plate 68 is disposed against the outerside of the blade 65, the contact therebetween is subtantially a linecontact extending lengthwise of the blade 65 and about midway betweenits opposite longitudinal edges.

The keeper plate 68 has riveted thereto a pair of studs 69 locatedadjacent to its opposite ends, the studs projecting through the same andterminating at a substantial distance from the concave side thereof.Next to the concave side of the keeper plate 68, the studs 69 areprovided with an enlarged circular body 70, forming an annular shoulderH abutting against the inner arcuate face of the keeper plate. The blade65 is provided with circular apertures adjacent to its opposite ends,which snugly receive the enlarged circular bodies ID on the studs 69, aswill be obvious from reference to Figures 6 and '7. The enlarged bodiesTil are of substantial length and are provided with flats 12 on oppositesides so as to fit in the slots 63 of the reciprocal blade 5'! andthereby guide the blade 51 in its reciprocal movement. As shown in thedrawings, the length of each slot 63 in the blade 51 is slightly greaterthan the diameter of the enlarged portion 10 on the studs 69, plus thethrow of the operating lever 14, the latter being preferably on theorder of .038" at each side of its central or neutral position. Thisallows the reciprocal blade 51 to freely move the full stroke of .076"without interference, while its movement is accurately guided by thesubstantial contact of the flats 12 with the long edges of the slots 63.

The head 5 is suitably apertured to receive the inner extremities of thestuds 69, and the outer face of the head is recessed, as at 13, toreceive the inner extremities of the enlarged bodies 10 on the studs.The depth of the recesses 15 should be great enough to allow for axialadjustment of the studs 59 relative to the head 5 as when adjusting tnetension of the blade 65 against the blade in in a manner now to bedescribed.

The inner end of the leg 52 of the head 5 is socketed, as at 14, to asubstantial depth coaxially with the openings which receive the studs68, these sockets being adapted to loosely receive internally threadednuts 15 which screw onto the inner threaded extremities of the studs 69,as will be best understood from reference to 'n'igures 5, 6 and 7. Theinner threaded extremity of each of the studs 69 is preferablydiametrically slotted, as at 16, and its nut 15 is diametricallyapertured to receive a lock-pin 11 adapted to be inserted through atransverse opening 78 in the leg 52 of the head 5, the opening 18registering with the diametrical opening in the nut "i5 when the latteris turned to the proper position. The lock-pins l1, one for each stud69, are preferably loosely disposed in the openings previously describedso that they can be readily removed to permit adjustment of the nuts 15when the head 5 is removed from the handle I. However, in the assembledcondition of the shaver, the lock pins are inaccessible and unnecessarytampering with the tension adjustment of the blades is minimized.Obviously, when the head 5 is removed from the handle I, and the lockpins 1! withdrawn, the nuts 15 may be turned in one direction to causethe studs 59 to be drawn inwardly of the head 5, thereby moving thekeeper 68 relatively closer to the outer end of the head andcorrespondingly increasing the tension of the blade 65 against the blade51. Turning of the nuts 15 in the opposite direction effects acorresponding reduction of the blade tension. Once the tension has beenset properly, as when the shaver is assembled at the factory, it may beindefinitely maintained uniform without any need for further adjustment,excepting under unusual or abnormal circumstances. As previouslymentioned, the tension adjustment of the blades 65 is preferably suchthat the lapped surfaces 66 of the blade 65 have substantially fiatcontact with the upper fiat side of the relatively rigid reciprocalblade or shear plate 51. By reason of the fact that the keeper B8 bearsagainst the blade 65 with substantially a line contact at the center ofthe blade, the blade 65 can flex transversely the full distance from thecenter of the blade to its opposite longitudinal edges. This ma teriallycontributes to the accuracy of adjustment of the tension and themaintenance of a substantially uniform tension indefinitely.

The cutting instrumentalities of the relatively reciprocal blades 51 and65 are so disposed with relation to the outer extremities of the guardor guide ribs 59 at the opposite longitudinal sides of the head 5 thatthe shaver may be moved over the skin without discomfort, and willproduce a smooth, close hair clipping or shearing action, yet withoutpinching the skin between the edges of the blades and the guard ribs orotherwise scratching or abrading the skin, Th blades or shear plates aresubstantially selfcleaning and will not clog up by reason of theprovision of the grooves 55. Any hair which may collect or which doesnot automatically fall out of the grooves 55 may be readily removedtherefrom in an obvious manner.

By reason of the relation of the bl d or shearing plates as hereindisclosed, it has been found that it is perfectly possible and practicalto employ blades of a thinness which heretofore could not be employedwith any degree of success in shavers of this general type. Moreover,the provision of the beveled cutting edges on the reciprocal blade 51and the beveled edges of the transversely arcuate flexible blade 65resulting from lapping the flat surfaces 56, enable the cutting edges ofthe coacting teeth 64 and 61 to be brought closer to the skin at thebase of the hairs and thereby cleanly severing the hairs at a pointhaving the optimum closeness to the skin, which has heretofore beenunattainable in a power driven shaver.

In the use of the shaver, it is drawn over the skin with the guard ribs59 pressing lightly against the same, the latter being so formed as toglide over the skin with a smooth and pleasing feeling, while thecontiguous teeth 64, 61 of the relatively reciprocal blades are disposedin a position to clip the hairs in an obvious manner. As the shaver isdrawn over the skin, the hairs are guided into the teeth of the bladesby the comb effect resulting from the transverse slotting of the guardribs 59. These transverse slots or kerfs fill in the ribs 58 arepreferably arranged directly opposite the indentations between the teeth6'! of the stationary blade 65 whereby to facilitate the guiding of thehairs into position to be cut by the blades or shear plates.

While the specific details have been herein shown and described, theinvention is not confined thereto as changes and alterations may be madewithout departing from the spirit thereof as defined by the appendedclaims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is- 1. A device of the class described,comprising a support, a pair of thin relatively reciprocable bladesmounted thereon, each having shearing instrumentalities on at least oneedge thereof, one of said blades being relatively rigid and flat, andthe other of said blades being flexible and normally transverselyarcuate in its inert condition and being bevelled along the edge in thezone of its shearing instrumentalities to provide a substantially flatsurface having substantially flat bearing contact with the other bladein the zone of the shearing instrumentalities, and means forcontinuously urgin the blades into contact with each other in the zoneof the shearing instrumentalities aforesaid while impartingreciprocating motion to one of said blades.

2. A device of the class described, comprising a support, a pair of thinrelatively reciprocal blades mounted thereon, each having shearinginstrumentalities on at least one edge thereof, one of said blades beingrelatively rigid and flat and being beveled on one side in the zone ofthe shearing instrumentalities, and the other of said blades beingflexible and normally transversely arcuate in its inert condition, saidlatter blade being bevelled along its edge in the zone of its shearinginstrumentalities to provide a substantially flat surface adapted toengage the first blade in the zone of the shearing instrumentalities atits flat side which is opposite to the beveled side.

3. A device as claimed in claim 1, wherein the last named means includespressure means acting upon the transversely arcuate blade substantiallyat the center thereof along a line extending generally parallel to theedge of the blade on which the shearing instrumentalities are provided,for pressing the arcuate blade against the other blade.

4. A device as claimed in claim 1, wherein the means for urging theblades into contact with each other comprises a keeper plate having atransversely arcuate face, the radius of which is somewhat greater thanthe radius of the transversely arcuate blade, said keeper plate servingto produce pressure substantially on a line at approximately the centerof the transversely arcuate blade, while permitting said latter blade toflex from the center to its edge which is provided with the shearinginstrumentalities.

5. A device as claimed in claim 1, wherein the means for urging theblades into contact with each other comprises a keeper plate having atransversely arcuate face, the radius of which is somewhat greater thanthe radius of the transversely arcuate blade, said keeper plate servingto produce pressure substantially on a line at approximately the centerof the transversely arcuate blade, while permitting said latter blade toflex from the center to its edge which is provided with the shearinginstrumentalities, and means for varying the distance between the keeperplate and the relatively rigid fiat blade, whereby to vary the fieXureof the transversely arcuate blade and consequently the tension of thesame upon the relatively rigid flat blade.

6. A device of the class described comprising a rigid body constitutinga support, a generally rectangular thin flat blade mounted on one faceof said body in slidable engagement therewith, said blade havingshearing instrumentalities provided on at least one longitudinal edgethereof and having an elongated substantially rectangular slot thereinadjacent to each of its opposite ends, a second blade disposedcontiguous to the outer face of the first blade, said second blade alsobeing thin and flexible and generally rectangular in contour, withshearing instrumentalities provided on a corresponding longitudinal edgethereof, but being normally transversely arcuate in its inert conditionand bevelled along its edge in the zone of its shearinginstrumentalities to provide a flat surface for engagement with thefirst blade in the zone of the shearing instrumentalities of the latter,a keeper plate disposed against the outer face of the second blade andcontacting therewith only along the longitudinal center line of thelatter, a pair of studs respectively fixed to the keeper plate adjacentto the opposite ends of the same and projecting through both blades intothe body aforesaid, said studs passing through the elongated slots ofthe first blade and having fiat surfaces engaging the opposite sides ofthe slots to permit longitudinal movement of the first blade whilerestraining the same against transverse movement, nuts recessed in thebody and threadedly engaging the respective studs for adjusting thekeeper plate towards and away from the body to impart a predeterminedtension between the engaging surfaces of the blades, and means forimparting reciprocating motion to the first blade in the longitudinaldirection of the latter to produce a shearing action in the zone of theshearing instrumentalities on the blades.

OSCAR C. KAVLE.

